Variable condenser



May 7, 1929. M. SKRIVANEK VARIABLE CONDENSER Filed NOV. 28 1925 2 Sheets-Sheet y 7, 9 M. SKRIVANEK 1,712,359

VARIABLE CONDENS ER Filed Nov. 28, 1925 2 Sheets-Sheet 2 Ai FORNEY Patented May 7, 1929.

UNITED STATES 1,712,359 PATENT OFFICE.

MILES SKRIVANEK, OF CHICAGO, ILLINOIS.

VARIABLE CONDENSER.

Application filed November 28, 1925. Serial No. 71,986.

This invention relates to variable condensers, and more particularly to a variable condenser especially adapted for use in radio work.

One of the main objects of the invention is to provide a variable condenser the capacity of which can be accurately adjusted within very small limits so as to obtain a very accurate adjustment and permit fine tuning of radio apparatus in connection with which the condenser is used. A further object is to provide a condenser having means whereby the plate elements of the rotor can be successively moved into operative relation to the plate elements of the stator permitting the capacity of the condenser to be varied within a wide' range, very slight changes in the capacity being rendered possible for accurate tuning. Further objects will appear from the detailed description.

In the drawings:

Fig. 1 is a side view of a condenser constructed in accordance with my invention.

Fig. 2 is an outer end view of the condenser.

Fig. 3 is a section taken substantially on line 3 3 of Fig. 1, parts being shown in elevation.

Fig. 4 is a section taken substantially on line 4.4 of Fig. 3.

Fig. 5 is a section taken substantially on line 5-5 of Fig. 3.

Fig. 6 is an end view of the hub and the rotor member carried thereby.

Fig. 7 is an end view of the stator member.

The condenser includes end frames, 1 and 2 which, for convenience of description, will be referred to as the inner and outer frames, respectively. Each frame is of approximately three quarters circular outline and is provided at each end with an arm 3 having a foot 4 by means of which the frame can be secured to a panel or other suitable support, screws being passed through the feet 4 or the feet being secured by other suitable devices. The frames are secured in spaced parallel relation by rods 5 passing through the frames and through sleeves 6 preferably formed of electrical insulating material, nuts 7 being threaded onto the ends of the rods and bearing against the outer faces of the frames. Each frame is provided with an inwardly projecting lug 8 and strips 9 of electrical insulating material are secured to these lugs by screws 10 or other suitable means. These strips support the stator member 11 by means of wings 12 formed integral with and pro ecting laterally of this member, securing screws13 passing through the strips 9 and wings 12, and nuts 14 being threaded onto the lower ends of these screws. The stator member is of helical formation, the convolutions 15 of this member forming plate elements adapted to receive between them the plate elements comprised of the convolutions of a helical rotor member. A rotor member 16 is carried by a hub 17 which is mounted on the enlarged hexagonal portion 18 of an operating sliaft'18 which is rotatably mounted through a supporting ring 19 provided at the center of the outer end frame 2. The shaft is provided, adjacent the outer end of portion 18 with an annular flange 20 between which and supporting ring 19 is confined a spring washer 21. Inward movement of'the shaft through ring 19 is prevented by a stop cpllar 22 secured on the shaft by a set screw 23. This provides simple and efficient means for holding the shaft in rotary adjustment while permitting ready turning thereof.

Hub 17 is provided with a reduced exteriorly threaded neck 24 extending inwardly from the hub, this neck being provided with a hexagonal bore 25 extending from the enlarged bore 26 of hub 17. The bores 25 and 26 of neck 24 and hub 17 snugly receive the reduced hexagonal portion 27 and the enlarged portion l8,-respectively, of shaft 18. In this manner the hub is mounted upon the shaft for turning movement therewith and is free for sliding movement in either direction longitudinally of the shaft. Neck 24 operates in a sleeve 28 at the center of the inner end frame 1, this sleeve being bored and threaded for reception of the neck. The pitch of the threads of neck 24 are such that when shaft 18 is turned through one complete revolution the hub 17 will be moved in the direction of its axis a distance corresponding to the space between two adjacent convolutions or plate elements 16 of the rotor member 16. The stator member is so disposed, and the convolutions 0f the stator member and the rotor member are so related that the rotor member can be threaded into and out of the stator member with its convolutions or plate elements in proper spaced relation to the plate elements or convolutions of the stator member. When the shaft 18 is turned in one direction it will feed or thread the rotor member into the stator memher and, simultaneously with this turning movement of the shaft, the hub 17 will be moved a proper distance longitudinally of the shaft by means of the threaded neck 24 and sleeve 28. Preferably the pitch of the threads of the neck 24 is such that the rotor member will be advanced one plate element or convolution for each complete rotation of the shaft. In this manner the plate elements of the rotor are successively moved into. and out of operative relation to the plate elements of the stator member. This renders it possible to effect minute variations in the capacity of the condenser so as to obtain very accurate and fine tuning of the apparatus in connection' with which the condenser is used. In effect, I obtain a continuous ver nier effect of the condenser in that the number of plate elements or convolutions of the rotor member which are effective at any given time can be varied to suit conditions and, in addition, very minute adjustments may be made of the plate elements or portion of the rotor member which is in operative relation to the plate elements of the stator member. Preferably, though not necessarily, to insure good electrical connection between the shaft 18 and the hub '17, I provide a pigtail connection 29.

As will be understood, and as above indicated, changes in the construction and arrangement of parts of the invention may be resorted to without departing from the field and scope of the same, and I intend to include all such variations as fall within the appended claims, in this application in which a preferredform only of my invention is disclosed.

What I claim is:

1. In a variable condenser, a helical stator member, a rotatably mounted shaft, a hub mounted on said shaft for turning movement therewith and freely slidable longitudinally of the shaft, the hub being provided with an exteriorly threaded neck, a fixed sleeve, threaded connections between said sleeve and the neck for moving the hub longitudinally of the shaft in accordance with rotation thereof, and a rotor carried by the hub comprising a "plate wound into a helix whereby said plate may be moved into and out of operative relation to the helix of the stator by rotation of the shaft in proper direction.

2. A variable condenser including a stator comprising a plate wound into a helix with the convolutions thereof spaced apart a predetermined distance, a rotor comprising a plate wound into a helix with the convolutions thereof spaced apart a predetermine distance, a rotatable shaft held against longitudinal movement, a hub mounted on said shaft for turning movement therewith and freely slidable longitudinally thereof, said hub having an externally threaded neck, a fixed sleeve, threaded connection between said sleeve and the neck for moving said hub longitudinally of the shaft in accordance with the direction of rotation thereof, the pitch of said threads being equal to the helix of the stator and rotor plates causing said plates to operatively intermesh in'varying amounts dependent upon the longitudinal position of said hub.

3. In a variable condenser, in combination, spaced apart end plates, a rotatably mounted polygonal shaft, means associated with one of said end plates for holding said shaft against longitudinal movement, a hub having a polygonal opening formed axially therein, said hub being mounted on said polygonal shaft so as to be rotatable therewith and slidable longitudinally thereof, a sleeve carried by the other of said end plates, means associated with said sleeve and said hub for causing longitudinal movement of said hub upon the rotation of said shaft, a helical stator fixedly mounted between the end plates, a helical rotor carried by the hub, said helices being adapted to intermesh in varying amounts dependent upon the longitudinal position of said hub.

4. In a variable condenser, in combination, spaced apart end plates, dielectric strips carried by said end plates, a plate wound into a helix fixedly mounted on said strips, a hub, a plate wound into a helix mounted on said hub for rotary movement therewith having helix thereof of the same pitch as the helix of the fixedly mounted plate and' being adapted to intermesh with ,said fixedly mounted plate in varying amounts depend; ent upon the longitudinal position of the hub, a rotatably mounted shaft, said hub being mounted on said shaft for turning movement therewith and slidable longitudinally thereof, and a sleeve carried by one of said end plates and adapted to screw threadedly engage said hub whereby to move said hub longitudinally along said shaft upon the turning of said shaft.

In testimony whereof I afiix my signature.

MILES SKRIVANEK. 

